The overall objective of the proposed research is to elucidate in molecular terms the mechanisms by which purified natural and cloned human leukocyte (IFN-alpha) and immune (IFN-gamma) interferons act to affect a wide variety of fundamental viral and cellular processes. The specific aims are as follows: (1) To elucidate the structure function of polypeptide p54, a protein efficiently induced by IFN-gamma in human cells, but poorly, if at all, induced by IFN-alpha. Biochemical and immunological characterizations suggest that p54 may be a cytoskeleton-associated polypeptide. We plan to attempt to obtain a molecular clone of p54 and to use the clone and antibody as reagents to elucidate the function of p54 and its possible role in the antiviral effects of IFN-gamma. (2) To attempt to elucidate, by combined molecular genetic and biochemical approach, the molecular basis of the antiviral effects of human IFN-alpha exerted at the level of protein synthesis. Reovirus and vesicular stomatitis virus are inhibited by IFN-alpha in several cell lines at the level of mRNA translation. The expression of cDNA copies of reovirus and VSV genes is likewise inhibited by IFN-alpha, but not IFN-gamma, in transfected simian cells at the level of protein synthesis. We plan to construct mutant reovirus cDNA expression vectors, and to study the effect of IFN on reovirus protein synthesis in transfected cells. (3) To continue our efforts to determine the biochemical basis, both in vitro and in vivo, of the difference in translational efficiency of the s-class mRNAs of reovirus. The rate of synthesis of the individual omega-class polypeptides differs significantly under conditions where the molar amount of the four sigma-class mRNAs differs by less than 2-fold. To attempt to identify the RNA binding domains of polypeptides omega NS and omega 3, and the function of polypeptide p12, products of reovirus class genes. The health relatedness of the proposed research stems from the likelihood that the work may contribute to a better understanding of regulatory mechanisms possibly operative in normal cells as well as virus-infected cells, and that the elucidation the molecular mechanisms of action of the different types of interferons is of immediate important in view of the potential application of IFN in the clinic.